Statistical Reasoning & Practice, Week 4 Notes
Statistical Reasoning & Practice, Week 4 Notes 36-201
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This 2 page Class Notes was uploaded by Monica Chang on Friday September 23, 2016. The Class Notes belongs to 36-201 at Carnegie Mellon University taught by Gordon Weinberg in Fall 2016. Since its upload, it has received 18 views. For similar materials see Statistical Reasoning and Practice in Statistics at Carnegie Mellon University.
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Date Created: 09/23/16
Week 4 Outline of randomized comparative experiment: - Ex. Seeing if taking vitamin c pills affects duration of sickness - If we used randomized assignments we are conducting an experimental study, otherwise it’s an observational study. - Key components of simple randomized comparative study: 1. Randomized selection and randomized assignment: - Random selecting eliminates bias (systematic error) - Random assignment eliminates lurking variables 2. Placebo control group: - Giving a “non-active” treatment to avoid placebo effect 3. Double blind: - When both the subjects and the researchers interacting with the subjects do not do not know what treatments the subjects are getting 4. Sufficient sample size: - Reduces random variability - Increases statistical significance (i.e. when an effect is real, rather than due to sampling variation) Matched Pairs study: alternative study design for CQ relationship: - Two explanatory treatments, each subject gets both treatments - For analysis, the “matching” treatments are compared - Matched pairs design is usually used when there is natural pairing involves (e.g. pre-test/post-test, twins, etc.) When to use a matched pairs study as opposed to a simple randomized comparative study: Example: Does meditating for 5 minutes help you do better on an exam? - Randomized comparative study: o Random selection from population, randomized assignment of sample, treatment: meditation before exam, control group: not, compare exam scores between groups, o Issues w/ this using this method in this case: Magnitude of difference is likely smaller than random variation There is not way to create a placebo control group for not meditating - Matched Pairs study: o Everyone takes 2 tests, one without prior meditations another without prior meditation o Make a table with first test score column and second test score column, and compare “matching” scores
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